Depression of copper minerals from ores and concentrates



Patented Dec. 2, 1952 UNITED STATES PATENT DEBRESSIQNQE COPPER MINERALS F-RQM. oR sA -n CONCENTRAFIJES.

Charles Francis Allen V and Robert Ben Booth... Stamford, Conn., assignorsto Am rican Cyana mid Company, New York,

of Maine umeration..

N0 Drawing. ApplicatiomAugust 16,1951, Serial No. 242,184:;

15 Claims. (01109-4 7),

This invention relateste an improved proeess oth flota ion 0 ulfide re and mor partic ularly for the depression of E cppper minerals in such processes.

Differential flotation processes for the beneficiation of sulfide minerals-have been used extensively, The mest common; processes involve the treatment of lead zinc oresand: lead-copper zinc ores and dependon the depression of zinc and;

am. acceptable. houshnot ideal selution with.

ertain. of h se. mi e t ores.- Certa n. nqx eanie, phqspha e cm i nds h v se en sedefie w vely s. epress ntsin h separation of; c p er; sulfides from molybdenum sulfides.

Attempts have been; Ir 1ade. to depress copper minerals inlead copper and copper-molybdenum concentratesby the use of cyanides. However, d na y e desw a e ee ite d let n s inc' ulfides v i her. 9 se et i e. actionin the case of lead-copper concentrates or are too weakly selective to beef practical'utility.

According to the present invention, we have found with a certain, combination involving certain metals, the cyanide radical and, ammoniain a particular state of combinationhave great selec: tive depressant power for copper minerals, With:- out seriously depressing either lead or molybdenumsulfides. The combination requiresthe cyanideradical, a metal selected from the group con: sisting of magnesium, zinc and aluminum, and, ammonia in the form of a free base. When these three conditions are satisfied, good selective desam action r c et vlfidss a ach e ed;

1 5 o n n. h 11? ar icu ar l ll izalt The salt-like chemical union 0i the ammonia with the cyanide defeats. any depressing a As the exact reason fonthe peculiar require for, the. depressant ofwthe presen QY l PH known, no theory, is advanced as .to why theciepre ant of h re en .i iyentiqnt as n N and the invention is notin tended tg be to any theoretical explanations A wid n mbe dm qliadser mixiutes ay, b us b or hemesen nveutien, o x

p e e. meta fl e r entl a alti 'i cyanide as analkaiine metal-or a l' ali e eaifth,

f t w n d aaqf h m ti n sammleniu hydroxide or compounds liberating itlinlfiotation' operation. This mixture, which ,may' p act in thefiota tion pulp, gives satisfae or sion. It is also possible to associate the am v with either the metal compound or: with the cyanide. Thus, for e ample, 'a saitoi zinc; mage ium or umin mmay-he reatedwl thsa ammonia with resultant absorption of arnm n in m w i is, appar n ly. mtmrmel. cally bound as acomplexsalt, and this ammo tmercially av i able c anidesnvol es.amm at naWe yani and ith. a a t. 4 magnesi m, r flui mnf The fourth method, which produces the cheapest and most active depressant, involves the am moniating of zinc cyanide. This fourthprocess is not applicable to "depressants inwhich tliel metal is aluminum because of the notabl in stability of aluminum cyanide.

The proportions of the ingredients are not critical. It is. desirable to. operate. with, equimo lal amounts of the metal and: cyanide.

widely and usually is determinedby the amount of ammonia which either the metalsaltor the cyanide will take up.

The totalamount of depressants willvary and is usually figured on the metal cyanide mole equivalent from 2-to 5 lbs/ton of flotation feedranges, there being no sharp. cut-off. Amounts.

below '2, lbs/ton of feed, show a fa11ing..-.ofi in depressant action which soonimakesttheioperae tionuneconomical. On the. otherhand, particu, larly 1n the case of lead-copper. concentrates,

depression. of. lead sulfides occurs. when the.

I In mostcases. I there i no erlous loss, of, lead up. to 5. lbs/ton.

amount of depressant isexcessive.

hird iii 'd it The. amountof ammonia in the basic form mayvary.

of feed but the upper limit will vary somewhat with difierent ores and different concentrates.

The invention has been described in connection with concentrates containing lead and copper sulfides or lead and molybdenum sulfides. It is not limited to concentrates from ores which contain no other metals. Thus, for example, when a lead-copper concentrate is obtained by the froth flotation of lead-copper-zinc ores using the conventional ordinary cyanides as Zinc depressants, such a concentrate can be treated by the present invention with the same eflectiveness. In general, the process of the present invention is of particular interest in the treatment of concentrates. It is, however, not limited thereto, and in certain cases may be used with the original ore. Ordinarily this is less desirable as the reagent consumption based on the amount of copper and lead present is higher than when concentrates are treated, particularly if the ore is not very high grade.

It is an advantage of the present invention that the flotation operation itself is not changed by the use of the depressants of the present invention. Thus, the ordinary collectors for copper and lead sulfides such as xanthates, dithiophosphates and the like may be used with conventional frothing agents. Ordinary froth flotation operating techniques are also followed, a number of flotation machines in a string, period of flotation in each machine, cleaning and recleaning of concentrates where necessary, all follow along conventional lines and no new operating techniques need to be learned in order to obtain the advantages of the difierential flotation which forms the subject matter of the present invention.

As has been pointed out above, some of the depressants of the present invention are physical mixtures and others single constituents. In the case of some of the latter the depressants are themselves new compounds and in a more specific aspect of the present invention are included.

The invention will be described in greater detail in conjunction with the following specific examples, which illustrate typical modifications of the present invention used with representative ores.

All flotation tests were effected in laboratory Fagergren flotation machines under normal flotation conditions:

Example 1 Concentrates from a South African lead-copper ore were prepared, havin an average assay of about 56.5% lead and 12% copper, the ratio of concentration being approximately three to one. The concentrate was prepared using 0.1 lb./ton of sodium isopropyl xanthate and 0.07 lb./ton of a higher alcohol frother averaging 7 carbons in chain length. The reagents adhering to the concentrate were sufficient to act as a collector-frother for the lead in the succeeding operation. No additional reagents were required.

The concentrate was conditioned with 6 lbs. /ton of ammoniated zinc cyanide which was prepared by ammoniating zinc cyanide with gaseous NI-Is, producing a product having the composition ZI1(CN)2.1.8NH3. The concentrate was conditioned and floated in a flotation machine with 0.06 lb./ton of paraffin alcohol averaging seven carbon atoms as a frother to produce a rougher lead concentrate. The concentrate was then conditioned with 0.6 lb./ton of zinc cyanide am- 9 lbs/ton of ammonium phosphate.

'4 moniate and 0.06 lb./ton of frother floated to produce a cleaner concentrate.

The ammoniated zinc cyanide may vary in its ammoniated content over a wide range without materially aifecting flotation results.

Example 2 The concentrate of Example 1 was conditioned with 13.8 lbs/ton of zinc cyanide and 7.5 lbs/ton of ammonium hydroxide containing 25% NHs, 0.06 lb./ton of the frother of Example 1 was added and a rougher concentrate obtained.

Example 3 The concentrate of Example 1 was conditioned with 21.8 lbs/ton of crude calcium cyanide sold by the American Cyanamid Company as Aero Brand cyanide, 25 lbs/ton of ZnSOnI-IzO and 0.03 lb./ton of frother was then added and a lead concentrate obtained by froth flotation.

The cyanide used contains a large excess of lime which reacts with the ammonium phosphate to liberate ammonia.

Example 4 Example 5 A concentrate of Example 1 is conditioned with 19 lbs/ton of zinc sulfate, 12 lbs/ton of sodium cyanide and 7.5 lbs/ton of 25% ammonium hydroxide. 0.06 lb./ton of frother was added, and a lead concentrate obtained by froth flotation.

Example 6 The concentrate of Example 1 was conditioned with 5.1 lbs/ton of Aero Brand cyanide and 4.5 lbs/ton of zinc chloride ammonia/ted to take up 4 mols of ammonia. 0.06 lb./ton of frother was then added and a lead concentrate floated.

Example 7 The concentrate of Example 1 was conditioned with 5.1 lbs/ton of Aero Brand cyanide, and 7.2 lbs/ton of zinc sulfate ammoniated to take up l moles of ammonia. 0.06 lb./ ton of frother was then added and a rougher lead concentrate floated. This was then cleaned after the additional 0.06 lb./ton of frother, and a cleaner concentrate obtained.

Example 8 The concentrate of Example 1 was conditioned with 3.1 lbs/ton of Aero Brand cyanide, 4.2 lbs./ ton of MgClz-Gl-IzO ammoniated to add 25% ammonia by weight. 0.06 lb./ton of frother was then added and a lead concentrate floated.

Example 9 The concentrate of Example 1 was conditioned with 3.1 lbs/ton of Aero Brand cyanide and 5.3 lbs/ton of MgSO4-7H2O ammoniated to take up aceogoeez r 37 .ripantsiby .weightirof (ammonia... oiodalbz/tonof frother was then added and allead;concentrate.

Example 11 The concentrate .of Example. 1 was conditioned with 1 1.6: lbs./ton of. ammoniated Aero. Brand."

cyanide prepared as. described 3 in the preceding example and 10.8 lbs/ton of ZnSO-i-YHzO: 0.06 lbi/toncf frothergwasthcn added-and a leadconcentratethen floated.

Example-12 The concentrate of Example 1 was conditioned with 5.8 lbs/ton of ammoniated Aero Brand cyanide prepared as described in Example 10 and '7.31bs./ton of ammoniated zinc sulfate prepared as described in Example 7. 0.03 1'b./ton of frother was added and a lead concentrate floated.

Metallurgical results of Examples 1 to l2are shown in the following table which also includes controls. where cyanide zinc oxide were used and.

where cyanide and ammonium hydroxide were used. In the column under depressant, Aero Brand cyanide is abbreviated ABC, zinc magnesium and aluminum salts are written without water of crystallization. Ammoniation is indicated by NH3. The assays are given for the final lead concentrate. This is the rougher concentrate in some examples, and the cleaner concennor-additional.collectorwas required; Thesresulte 3 ing :leadz: concentrate: was ":cleaned torgiveta: final. concentrateassaying 26.7%: Pb: and 17.9%" Cu; with a leadrecovery of. 80.7

Example 14 Ar copper: molybdenum concentrate. from. a southwestern. ore: having an average assays of: about 1*.85.% 1 molybdenitev: and-1.30% copper? was conditioned I with 4 r lbs/ton 1 of ammoniatedgzinc cyanide prepared as described in Example :5 and: 0.04'Ilb./ton of a higher alcohol frother :stabilized with. fuel oil; which also acts asza. molybdenite collector; as ;well as a frother. A.m-olybdenum concentrate was-floated. which Wasscleaned. and; recleaned. An additional 2.0 lbs/ton". of; am moniated zinc cyanide was addedxduring thetflrst float and first. cleaner fioa-t and@1.0.lb./ton.dur.e ing the recleaner float. Eachfloat.hadthesa/me. amount of fr-other added; 0.04 Ila/ton.

A molybdenite concentrate was obtained assaying 20.55% MOSz Cu. The percentagadistribur tion of MOSz was. 75.23inthe molybdeniteconcentrate.

When the concentrate of Example 14 was-con. ditionedrwith -lbs./ton of A-ero Brand? cyanide or 10 lbs. of Aero Brand cyanide and. 10 lbs. .of NH4OH no practical copper -depression.re sulted.

Example A copper molybdenite eoncentratefrom a Utah copper ore having an average assay (if-1.68% M082 and coppenpreparedby froth flotation using dicreseyl dithiophosphate as acollector; was conditioned with 5 lbs/ton of ammoniated zinc cyanide, prepared as described in Example 1, and then floated with 0.06 lb. of the frother of Example 13. The concentrate was cleaned 6 times, additional ammoniated zinc cyanide for trate where cleaning is described. the first float and six cleanings in pounds per Percent Dis- Assay tribution Example Depressant Pb Cu Pb Cu ZnGNh-NHa 72. 3 3. 4 82.1 18. 4 Zn GN)2;NH4OH 69. 7 4. 8 96.2 32. 4 ABhG;tZnS 0;;Ammom'um Phos- 65.1 5. 6 95. 6 39. 4

D 8. 6. AB(:ZnO;Ammonium Phos- 68. 4 3. 2 88. 4 18. 5

Z5 8 O4;NaCN;NH4OH 67. 4 6.0 95. 3 37. 8 ABC;ZnCl2;NHa 65. 2 6. 6 95. 5 47. 2

ABC;ZnS04;NHa- 71.7 4.0 81.8 21. 3 AB C;MgC1z;NH3 65. 9 6. 0 92. 7 40. 9 ABC;MgS O4;NHB.. 66. 1 7. 7 90. 7 51. 5 ABC;NHa;Al2 (S O4)s,NHs 70. 7 3. 6 90. 3 22. 5 ABC;NHz;Z11SO4 65. 7 5. 6 96. 1 40. 5 ABC;NH2;ZI1S 04;NH3 66. 4 6. 9 91. 1 44. 9 ABCZHO 47. 9 7. 6 4. 8 4. 53 NaCN;NH4OH Q) 1 All minerals substantially completely depressed.

Example 13 A copper-lead ore from a Chilean mine was ground and conditioned with 0.17 lb./ton of a collector which was a mixture of sodium mercaptohenzathiazole and sodium disecondary butyl dithiophosphate and 0.06 1b./ton of the 7- carbon atom alcohol frother used in previous examples. The conditioned pulp was floated to give a lead-copper concentrate assaying 9.5% Pb and 17.8% Cu; the ratio of concentration was 14 into 1. This concentrate was then conditioned with 8.0 lbs/ton ammoniated zinc cyanide prepared as described in Example 1 and floated to produce a lead concentrate. 0.06 lb./ton of the ton being as follows: 2.5, 3.0, 2.0, 1.0, 1.5 and none. Each flotation operation involved the addition of the same amount of frothe-r, 0.06 1b./ton. The distribution of molybdenite in the 6th cleaner concentrate was 83.1% and this concentrate contained 36.6% M082 and only 3.64% Cu, the remainder of the concentrate being a fine ser-icitic material. The copper product (the final tailing? contained only 0.05% MoSz.

We claim:

1. A process of selectively depressing copper sulfides in the presence of a sulfide included in the group consisting of lead sulfides and molybdenum sulfides which comprises efiecting froth alcohol frother u d in Examples was used; flotation in the presence of a collector for sulfides and from 2 to 15 lbs/ton of a depressant containing the cyanide radical, a cation selected from the group consisting of zinc magnesium and aluminum, and non-ionically linked ammonia.

2. A process according to claim 1 in which the copper sulfides are associated with lead sulfides.

3. A process according to claim 2 in which the depressant comprises ammoniated zinc cyanide.

4. A process according to claim 1 in which the sulfide associated with the copper sulfides is molybdenite.

5. A process according to claim 4 in which the depressant comprises ammoniated zinc cyanide.

6. A process according to claim 1 in which the depressant is a mixture of an ammoniated salt containing the cation and a soluble cyanide.

7. A process according to claim 6 in which the soluble cyanide is a crude calcium cyanide containing excess lime.

8. A process according to claim 7 in which the sulfides associated with the copper sulfides are lead sulfides.

9. A process according to claim 6 in which the sulfides associated with the copper sulfides are lead sulfides.

10. A process according to claim 1 in which the cation is zinc.

11. A process according to claim 10 in which the sulfides associated with the copper sulfides are lead sulfides.

12. A process according to claim 1 in which the cation is magnesium.

13. A process according to claim 12 in which the sulfides associated with the copper sulfides are lead sulfides.

14. A process according to claim 1 in which the cation is aluminum.

15. A process according to claim 14 in which the sulfides associated with the copper sulfides are lead sulfides.

CHARLES FRANCIS ALLEN. ROBERT BEN BOO-TH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Hoffman, Lexikon der Anorganischen Verbindungen, Band 1 (Nos. 1-31), pages 554, 558. Published by Verlag Von Johann Ambrosius Barth, Leipzig, Germany, 1917. 

1. A PROCESS OF SELECTIVELY DEPRESSING COPPER SULFIDES IN THE PRESENCE OF A SULFIDE INCLUDED IN THE GROUP CONSISTING OF LEAD SULFIDES AND MOLYBDENUM SULFIDES WHICH COMPRISES EFFECTING FROTH FLOTATION IN THE PRESENCE OF A COLLECTOR FOR SULFIDES AND FROM 2 TO 15 LBS./TON OF A DEPRESSANT CONTAINING THE CYANIDE RADICAL, A CATION SELECTED FROM THE GROUP CONSISTING OF ZINC MAGNESIUM AND ALUMINIUM, AND NON-IONICALY LINKED AMMONIA. 